An excavator used for mining minerals, particularly for continuous strip mining of minerals, can comprise a track drive, a digging unit with at least one digging roller and a connected conveyor for the raw ore or broken mineral matter formed in the mining operation. The digging roller has a roller core and at least one helical digging and delivery member or screw or worm flight.
A delivery mechanism which receives raw ore from the helical digging flight is mounted between the conveyor and the digging roller. The digging unit can be movable up and down and can also be pivotable about a vertical axis. Usually two digging rollers are provided which work opposing the delivery mechanism. On the outside of the excavator front end, additional digging rollers angled fordwardly can work with the above mentioned digging rollers.
As noted in the documents earlier referred to, a tunnel or gallery excavator is known. These can be employed only with some difficulty as strip-mining machines. The delivery mechanism comprises a loading apron and digging tool in the form of a digging arm or digging roller. The digging tool also guides the raw ore to the conveyor. When used in strip mining such machines cannot guarantee that the delivered raw ore component will not have a grain size which is too large and exceeds a predetermined minimum grain size. Such oversize pieces lead to an interference or disturbance in the flow of the raw ore, in its manipulation and frequently with its delivery.